Incorrect prerelease versions if `.gitversion` file contains default version number (0.1.0) does not exist

Environment: OpenTAP 9.7

Steps to reproduce:

1. Create/use git repo containing a .gitversion file with version = 0.1.0
2. run tap sdk gitversion on the master branch. Output is 0.1.0-beta.1
3. Make some change (not in the .gitversion file) on the master branch and commit it.
4. run tap sdk gitversion again. Output is still 0.1.0-beta.1

Expected result:

Output of tap sdk gitversion should increment N in X.Y.Z-beta.N on each commit as described here: https://doc.opentap.io/Developer%20Guide/Plugin%20Packaging%20and%20Versioning/#git-assisted-versioning